Piano construction



March 12, 1929. C, MEHUN 1,705,196

' PIANO CONSTRUCTION Filed Aug. le, 1926 V M V/ v 2/ E Z/l E 5.7M Mr M1 Patented Mar. l2, 1929.

UNITED STATES CHARLES MEHLIN, OF FORT LEE, NEW JERSEY.

PIANO CON STRUCTION.

Application led August 16, 1926.

This invention relates in general to a piano construction and has for an objectthe provision of a sound board construction and arrangement of increased strength and durability and improved tone quality.

An important object of the invention is the provision of a sound board that will not sag or warp and thereby lose its vibrating and tone qualities.

Another important object of the invention is to provide a sound board for a piano that is reinforced or povided with means for re lieving the sound board of the normal pressure of the strings and bridge so that the sound board will. be substantially free to vi brate or will freely vibrate in response to vibrati ons of the strings so that the tone of the piano will be of longer duration and will be more full, more clear, and of greater volume and carrying power.

Another important object of the invention is to provide a piano in which the sound board is formed to extend equal distances to each side of the main sting bridge and such a device in which the sound board is formed substantially in accordance with the human tone cavity. Y

Another important object of the invention is to provide a tone chamber beneath the sound board of a piano that is formed to amplify the tone `generated by the vibration of the strings in proportion. to the pitch of the string so that the tones generated by the higher pitched and weaker strings will be amplified in proportions to the Weakness or pitch of the string and such a device that is formed substantially in accordance with the human tone cavity.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description which taken in connection with the accompanyin g drawings illustrates a preferred embodiment thereof.

Referring to the drawings:

Figure 1 is a plan view of a piano with parts removed and embodying my invention;

Fig. 2 is a sectional view taken substantially on line 2-2 in Fig. l: and

Fig. 3 is a further enlaged view taken substantially on line 3 3 in Fig. 2 and showing the sound board and two stiffening ribs in cross section.

To illustrate my invention I have shown a Serial No. 129,350.

piano frame 1l, a sound board supporting frame or rim 12. a sound board 13, a string frame 11 and bridges 15. i The frame 11 may be of any suitable form and material such as that of an upright or grand piano, and I have shown the frame of a grand piano, merely to illustrate my invention. The supporting frame or rim 12, the sound board 13, the supporting frame 14 and bridges 15 are also constucted/in accordance with the design of the piano, and may be of any suitable size. The sound board 13 is preferably crowned slightly as shown (Fig. 2) and stiffening ribs 16 are provided that may be attached to the sound board in any suitable manner` such as by glue or with pegs or the like. The stiffening'ribs 16 may cX- tend across the sound boad in any desired direction and are preferably arranged at right angles to the grain of the sound board. Tliey are preferably of suilicient length to extend entirely across the sound board wherever used, but it will be noted that they may be somewhat shorter if desired. The ends 17 of the stiffening ribs 16 are preferably seated in the supporting frame or rim 12 as at 18 (Fig. 2) to vprovide bearings for the ribs.

In accordance with my invention the ribs 16 are of a relatively large cross sectional area at or adjacent their ends and of a reduced cross sectional area intermediate their ends. That is. the cross sectional area is preferably the least at or beneath the long bridge or at the center of the board and theY greatest at the supports. This may be accomplished by forming the ribs of uniform width and varied thickness or of uniform thickness and varied Width. In the present instance however, I have shown the upper surface 19 of the ribs formed to lit the sound board 13 and the lower surface 21 of the ribs curved on a somewhat smaller radius so that the thickness is gradually increased as the distance from the center of the board is graduallv increased or so that the thickness gradually decreases as the distance from the support gradually increases. The difference between theminimum and maximum thickness or cross sectional area should not be so great however, as to provide a. rigid construction, such as might prevent or materially reduce the vibrations, and is determined by the length of span and the normal pressure of the strings. It is an object of the invention to provide a balanced sound board that will yield to vibrations equally on each side ot the bridge and this regardless ot Whether or not the bridge located at the center ot the sound board and to provide a board in which the bridge and string sure is balanced by the strength oi the ribs and thus reduce the resistance to vibrations transmitted to the sound board and leave the sound board substantially tree to'vibrate just as it would it there were no string pressure on the bridge. The thickness ot the ribs tor this reason is determined by the pressure et' the. strings and the distance between the sound board supports. In constructing the bridge as shown, oner or more bridges l5 may be positioned on the sound board at any position between the supports, and the vibrations transmitted to the sound board through the bridge Will 'be of like strength and character, the tendency being tor the board to give at the point or" applicaiton et the forces, which is at the bridge, and tor radiate therefrom. The sound board being substantially free to vibrate Will uniformly distribute thel vibrations..

It is another important object to provide a tone chamber beneath or adjacent the sound board that is formed substantially in accordance with thehuma-n tone cavity in which the cross sectional area beneath each string is in proportion to the vibrating string or to the power ot the string to set air in motion so that the correct volume of air or space beneath each string is the amount that the string is able to set in motion to generate a uli round tone and such a chamber that Will amplity the tones generated by the strings in proportion to the volume ot the tone or pitch oi the strings so that the small strings having` a high pit-ch and relatively small tone value will be ampli tied to a high extent and the large strings having a low pitch and a large tone value will be only slightly amplitied, or not amplitied. To accomplish this the sound lboa-rd is preferably extended to substantiallyv equal distances on eachside ot' the main string l'iridge I5 and such distances that are in proportion to the length ot the string and closure member 31 is arranged beneath er adjacent the sound vboard and .spacedtherefrom to provide a tone chamber 32. The member 3l may be attached or supported Vupon the traine l2; in

any suitable manner and is 'formed substantially in accordance with the sound board 13. An opening 33 is provided that may be either inthe trames l1 and l2, the sound board l?) or the member 31, for establishing communication between the chamber 32 and the at- Y mesphere.v This opening may be ot' any suitable siZe and provided with volumel control devices ot any suitable type it desired. It will be noted that the strings to the right, viewing Fig. l, are the short and high pitched strings and the strings to the lett are the long and low pitched strings and that a section cut through a piano at either otthese strings will intersect the chamber and that the cross sectional area of the chamber in the point of intersection is in proportion to the length and pitch ot the strings and since the power oli the string to set air in motion is als-o in proportion to the length and size ot the string the correct amount ot space or air or just the amount that a string` will properly control or set in motion is beneath each string and further that since the chainber 32' tapered from arelatively small cross sectional area under the high pitched strings to a relatively large cross sectional area under the low pitched strings, the tones generated by the high pitched strings or by all strings are, or may be, amplified in proportion to the pitch of the string or vibrations.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be' apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention, or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim: f

1. In a piano, the combination of a'curved sound board, a support for the said board to support its periphery and bracing ribs extending under the board and supported in the sound board supports, the ribs being ot' uniform Width and curved to decreasing thickness adjacent the'bridge.

2. In a piano, the combination of a curved sound board, asupport thereforv engaging its edges, and bracing ribs extending under the sound board in Contact therewith, vthe ribs having bearings in and being supported by the sound board supports, the ribscurving to a diminished cross-sectional area adjacent the bridge.V y Y 3. In a piano, the combination of a string bridge, a curved sound board to support said bridge, a rim adaptedto support the edges of .the sound board, and sti lenin g ribs seated in y the rim, the ribs being of uniform Width and curved to a diminished thickness adjacentthe bridge. y

lt; In a piano, the combination of strings, a string bridge arranged in support thereunder, a curved soundboard for the strings supported by the bridge, a sound board support engaging the edges ofthe board and stiftening ribs extending under the sound board, the ribs being curved toy diminished cross-sectional area adjacenty the bridge and supported by bearings in the sound bridge support.

5. In a piano, the combination of strings, a string bridge therefor, the bridge being located near the curved center of the ribs, a

curved Sound board Supporting the bridge, a sound board support enga-,ging the edges thereof, and rims of varying cross-sectional area, stitfening and Supportitng the board borne .in the board supports, the crees-sectional area. being varied by two Curved. Surfaces, the greater area being' at the bearings and the lesser adjacent the bridge.

6. In a piano, the eonilriination of stringe, abridgl'e therefor, a Curved sound board Supported at its edges, curved stiii'ening ribs 'for the Sound beard having two surfaces of unequal curvature and a sound Chamber thereunder, the chamber being' open to the air and having a nonainiform cross-Sectional area.

7. In a piano, the combination of a curved Sound board, Strings arranged thereover, means to transmit vibratone of the strings to the board, a Closure member beneath the sound board and spaced therefrom to provide the tone chamber, the tone Chamber being ot nonnniferm Cross-sectional area.

8. In a piane, the combination of strings, a. String' bridge thereunder, a curved Sound board, a support for the board at. its edges, stiffening ribs for the board, the said ribs being' Supported in bea ringe .in the Sound board it supports and having ay Varying Crossseetional area.,` the greater area being at the lgiearinge and the lesser adjacent the bridge, the ribs harinjjT a uniform width and the depth Varying; between two unlike curved surfaces, and a eioeure member spaced from and under the sound board providing' a tone Chamber, the erosseeetional area of the tone chamber at any point therein varying' in proportion to the vibration Value of a string thereover, the said tone chamber being open to the air.

CHARLES MEHLIN. 

